ACEI

Dilated Cardiomyopathy: Poor Pump, An S3, and Crackles

virtualmedstudent

Cardiomyopathy = cardio (heart) + myo (muscle) + pathy (pathology). In other words, cardiomyopathies are pathologic processes that affect the heart muscle. Dilated cardiomyopathy, which this article is about, is the most common form of cardiomyopathy. It has some known causes, but interestingly the majority of cases have no known cause and may in fact be inherited. In order to be diagnosed with dilated cardiomyopathy you must have left ventricular dilation and a low ejection fraction on echocardiography.

   (1) Idiopathic (ie: no known cause) and/or genetic
   (2) Alcoholism (chronic)
   (3) Inflammatory
       (a) Infectious
           (i) Viral
                 1. Adenovirus
                 2. Coxsackie virus
                 3. Parvovirus
                 4. HIV
           (ii) Protozoan
                 1. Trypanosomiasis (Chagas’ disease)
       (b) Non-infectious
           (i) Collagen vascular disorders
           (ii) Sarcoidosis
   (4) Drug/medicine related
       (a) Chemotherapeutics (daunorubicin/doxorubicin)
       (b) Cocaine
       (c) Methamphetamines
       (d) Heavy metals
   (5) Metabolic
       (a) Hypothyroidism
       (b) Hypocalcemia (chronic)
       (c) Hypophosphatemia (chronic)
   (6) Neuromuscular diseases

Regardless of the cause, the left ventricle of the heart dilates, which decreases its ability to pump effectively.

Signs and Symptoms

The symptoms of dilated cardiomyopathy are directly related to the decreased pumping ability of the heart (ie: systolic dysfunction). Blood backs up into the rest of the body starting with the lungs. This causes pulmonary edema, which can manifest as orthopnea (ie: inability to sleep flat due to shortness of breath), dyspnea (ie: shortness of breath with exertion), and paroxysmal nocturnal dyspnea (ie: waking up in the middle of the night short of breath). Patients also complain of exercise intolerance, dizziness, and fatigue.

The physical exam for someone with dilated cardiomyopathy will often reveal an S3 gallop (aka: ventricular gallop). An S3 gallop is caused by excess blood in the left ventricle after systole; during diastole the blood from the left atrium rushes into a relatively full left ventricle creating the S3 gallop, which can be heard with a stethoscope.

In addition, “crackles” may be heard in the lung fields secondary to pulmonary edema. If right sided heart failure has also occurred (usually after many years of left sided cardiomyopathy) there may be signs of systemic volume overload. These signs include hepatomegaly (a larger than normal liver), bilateral lower extremity edema (ie: pitting edema), and jugular vein distension.

Diagnosis

Work Up for Dilated Cardiomyopathy
Echocardiography (ie: an ultrasound of the heart) is the gold standard test and will traditionally show a dilated ventricle(s) with a depressed ejection fraction (EF < 55%).

Additional studies can be ordered depending on the clinical scenario. It is especially important to not miss alcoholism or hypothyroidism as these can be easily treated. Cardiac catheterization is often performed to determine if there is co-existing (or causative) coronary artery disease.

Treatment

Treatment for patients with dilated cardiomyopathy consists of the similar treatments used for other heart failure patients. Many patients will be on an angiotensin converting enzyme inhibitor (ACEI, lisinopril is a commonly used one), or angiotensin receptor blocker (ARB) and a beta blocker (carvedilol is commonly used due to its beneficial lipid profile compared to other beta blockers). Other considerations include spironolactone (an aldosterone receptor antagonist).

ACEI/ARBs, beta blockers, and spironolactone improve survival rates in patients with dilated cardiomyopathy. In addition, an implantable cardiac defibrillator (ICD) should be considered in all patients with an ejection fraction of less than 35% because it has been shown to reduce death from abnormal heart rhythms.

Blood thinning medications like warfarin are indicated if the patient has a thrombus (ie: a “blood clot”) seen on echocardiogram, atrial fibrillation, or previous embolic event, although some physicians may recommend thinning the blood prophylactically if ventricular function is severely impaired (EF < 30%).

Symptomatic management consists of diuretics for volume overload (ie: pitting edema, shortness of breath secondary to pulmonary edema, etc.) and digoxin to increase cardiac contractility and improve forward blood flow.

Curative treatment is a heart transplant. Overall prognosis without a transplantation is poor. Over 50% of non-transplant patients are deceased at 5 years compared to 25% of transplanted patients.

Overview

There are many causes of dilated cardiomyopathy some of which are reversible. An S3 gallop and symptoms of volume overload are often seen on physical exam. Echocardiography is the gold standard for diagnosis. It is important to treat with at least a beta blocker and ACEI; spironolactone is another option. Symptomatic management includes diuretics and digoxin. Prognosis is poor without transplant.

Related Articles

References and Resources

  • Wexler RK, Elton T, Pleister A, et al. Cardiomyopathy: an overview. Am Fam Physician. 2009 May 1;79(9):778-84.
  • Abdo AS, Kemp R, Barham J, et al. Dilated cardiomyopathy and role of antithrombotic therapy. Am J Med Sci. 2010 Jun;339(6):557-60.
  • Fatkin D, Otway R, Richmond Z. Genetics of dilated cardiomyopathy. Heart Fail Clin. 2010 Apr;6(2):129-40.
  • Kumar V, Abbas AK, Fausto N. Robbins and Cotran Pathologic Basis of Disease. Tenth Edition. Philadelphia: Elsevier Saunders, 2004.
  • Lilly LS, et al. Pathophysiology of Heart Disease: A Collaborative Project of Medical Students and Faculty. Seventh Edition. Lippincott Williams and Wilkins, 2006.
  • Flynn JA. Oxford American Handbook of Clinical Medicine (Oxford American Handbooks of Medicine). First Edition. Oxford University Press, 2007.

Hypertension: Understanding and Managing High Blood Pressure

virtualmedstudent

The pathology of essential hypertension is not well understood. However, there are numerous theories, each with supporting evidence.

Genetic causes are supported by the fact that children of hypertensive parents have an increased risk of developing the disease. However, specific known genetic mutations are not common. When mutations are responsible for essential hypertension they often involve the sodium and chloride channels in kidney cells, or mutations in the genes responsible for producing the proteins of the renin-angiotensin-aldosterone system. Sodium, renin, angiotensin, and other molecules play a vital role in blood pressure. In some hypertensive patients these systems are abnormal and can lead to elevated blood pressure.

Some patients with essential hypertension appear to be “salt sensitive”. Salt, or more specifically sodium, appears to play a role in the development of hypertension. Some patients likely have a genetic predisposition to retain sodium. Excess sodium enters the blood stream where it exerts an osmotic pull on water in adjacent tissues. Fluid from body tissues is "sucked" into the blood stream resulting in increased blood volumes. The expanded blood volume increases the pressure within the blood vessel causing hypertension. Although salt plays a role in hypertension, new research has shown its importance may not be as clear as once thought.

There are other known causes of hypertension, but they constitute a relatively small proportion of cases. They are discussed in separate articles.

Signs and Symptoms

Essential hypertension in its earliest stages does not cause any signs or symptoms. Many people do not know they have high blood pressure. However, if left untreated hypertension can cause serious long term consequences.

One such consequence is an increase in the risk of cardiovascular disease. The risk of cardiovascular disease doubles with each 20/10 mmHg increase in blood pressure beyond a "baseline" of 115/75 mmHg! After years of pumping at elevated pressures the heart undergoes physical changes. Like any good muscle, it becomes larger because it is having to pump harder than normal. The result is a process known as concentric hypertrophy. The added muscle mass of the heart results in increased oxygen demand and the potential for heart attacks and heart failure.

Overall, nearly a third of heart attacks are attributable to high blood pressure. In addition, the risk of stroke is also dramatically higher in untreated hypertensive patients. The small blood vessels in the kidney and retina can also be damaged by years of high blood pressure resulting in kidney failure (hypertensive nephropathy) and blindness (hypertensive retinopathy).

Diagnosis

The diagnostic parameters of hypertension are constantly shifting. Currently the diagnosis can be made if a patient presents with a severely elevated blood pressure (systolic blood pressure > 200 and/or a diastolic blood pressure > 120) and/or signs or symptoms referable to the elevated blood pressure.

Severity Classification:
(1) Pre-hypertensive:
       130-140/80-90
(2) Grade 1:
       140-160/90-100
(3) Grade 2:
        >160/>100
In patients with less severe elevations, it is generally recommended that the blood pressure be measured several times over a period of multiple weeks. If the average of these readings is a systolic blood pressure of 140 or greater, or a diastolic blood pressure of 90 or greater than the diagnosis can be made. If the blood pressue stays between 120 and 130 systolic, and 80 to 90 diastolic the diagnosis of "pre-hypertension" is made meaning the patient is at risk of becoming hypertensive.

Some patients may have "white coat" hypertension simply by being in a doctor’s office (and the anxiety that this can provoke! Gosh, I hate going to the doctor’s office!). If this is the case the patient should be instructed to take their blood pressure at home and keep a log of the results.

Treatment

Treatment of hypertension consists of lifestyle modifications and/or using medications from several different pharmacologic categories. These medications may be used alone, or in combination, depending on each individual patient’s needs.

Patients who are pre-hypertensive or have stage 1 hypertension should be started on “lifestyle” modification therapy for at least 6 months prior to starting medicines (assuming there are no other health issues like diabetes or coronary artery disease). Lifestyle therapy consists of increasing aerobic exercise, as well as adhering to the “DASH” diet. DASH stands for "dietary approaches to stop hypertension" and consists of eating fruits, vegetables, low-fat dairy, whole grains, poultry and fish while reducing (or eliminating) red meat and sugars. This intervention alone can decrease systolic pressures over 10 mmHg and diastolic pressures over 5 mmHg.

Sometimes diet and exercise aren’t enough so we may have to resort to medications to control blood pressure. The first category of medications are known as diuretics, most commonly of the thiazide class. Thiazide diuretics work by inhibiting the re-absorption of sodium at the distal convoluted tubule of the kidney. Less sodium means less circulating blood volume, and therefore decreased blood pressure. Hydrochlorothiazide is a commonly used thiazide diuretic.

The second category of medications is known as β-blockers. β-blockers lower blood pressure by slowing the heart rate and indirectly lowering the amount of angiotensin II (angiotensin II is a potent natural blood vessel constrictor produced by the body). β-blockers reduce renin synthesis by specialized cells in the kidney.

A third category of medications known as angiotensin converting enzyme inhibitors (ACEIs) interfere with the formation of angiotensin II. ACEIs inhibit an enzyme present in the lung, which converts angiotensin I into the more potent vasoconstrictor angiotensin II. Interestingly, ACEIs also increase the level of bradykinin; this molecule causes blood vessels to dilate, which helps to further lower pressure.

There are also medications called direct angiotensin receptor blockers (ARBs), which inhibit the actions of angiotensin II. They do this by blocking angiotensin IIs ability to bind to its normal receptor sites.

Some medications, the calcium channel blockers (CCBs), lower blood pressure by inhibiting the contraction of smooth muscle cells that line the blood vessel walls. A specific subcategory of calcium channel blockers known as dihydropyridines block calcium from flowing into vascular smooth muscle cells. This results in decreased contraction of the muscle surrounding the vessel. As a result the vessel remains dilated, which lowers pressure.

Overview

The pathology of essential hypertension is not well understood. Several theories have been postulated, but it is likely a combination of genetic predispositions that result in this type of high blood pressure. Years of elevated blood pressure lead to cardiovascular disease including heart failure, heart attacks, and stroke, as well as damage to the kidneys and retinas. Treatment is with lifestyle modifications, diuretics, β-blockers, calcium channel blockers, angiotensin converting enzyme inhibitors, and angiotensin receptor blockers.

References and Resources